Traditionally, organ or tissue transplantation requires ABO blood type compatibility in order to prevent graft rejection. Normally, the host's blood contains circulating antibodies against foreign blood type antigens. Transplantation across these ABO blood groups leads to hyperacute rejection of the graft within the first 24 hours (Kuby J: Immunology. New York, W.H. Freeman and Company, 1997). Circulating antibodies bind to blood antigens present in red blood cells, epithelial cells and endothelial cells found in the graft organ or tissue. These antibody-antigen complexes activate the complement system of the host, resulting in infiltration of neutrophils into the graft organ or tissue. The neutrophils release lytic enzymes that destroy the graft endothelial cells, providing a surface of injured tissue to which platelets can adhere. Massive blood clots form within the capillaries, and this whole inflammatory reaction prevents vascularization.
Current treatments to reduce rejection include administering a regimen of immunosuppressant drugs before and after the transplantation surgery. Studies have been performed on methods that remove antibodies specific to ABO antigens. These methods have also shown beneficial effects in reducing hyperacute rejection of the transplanted organ or tissue. These methods are important because they may lead to a method which will relax the requirement of donor/recipient ABO compatibility, which in turn can greatly expand both the living donor and cadaver organ or tissue pools.
Current techniques to remove the ABO antibodies include plasma exchange combined with intravenous administration of soluble ABO antigens (Alexandre G P J, et al., Neth J Med, 28:231-234, 1985); separating plasma from the whole blood by either centrifugation or double filtration plasmapheresis (DFPP) followed by immunoadsorption using concentrated red blood cells (Slapak M, et al., Transplantation 31:4-7, 1981); and DFPP followed by column immunoadsorption of anti-A and B antibody using A and B antigen bound to silica beads (Tanabe K, et al., Transplantation Proceedings, 27(1) 1020-1023, 1995).
These prior art methods have serious problems which have prevented their adoption as the standard of care. First, there is the risk of infection. Because plasma exchange by centrifugation requires replacement by plasma protein solution, risk of viral transmission is present. Moreover, these techniques described above involve first separation of plasma from whole blood then an additional procedure to remove ABO antibodies from the plasma. Separated plasma can then be stripped of pre-existing anti-A and B antibodies by immunoadsorption with ABO antigens linked to silica beads on a column.
A study on renal transplantation has shown that ABO-incompatible grafted patients who received one or two sessions of DFPP and three or four sessions of column immunoadsorption showed no significant difference in survival rates when compared to patients who received an ABO compatible graft (Tanabe, supra). Additionally, one case has been reported in which hyperacute rejection following accidental ABO-incompatible renal transplant was reversed using plasmapheresis followed by immunoadsorption with red blood cells (Slapak, supra).